An embodiment of the present invention relates generally to integrated circuit fabrication. More particularly, an embodiment of the present invention relates to electrical connection technology. In particular, an embodiment of the present invention relates to a ball-limiting metallurgy comprising a copper layer.
Electrical bump connectors such as metal bumps or balls are used in flip-chip applications that may include controlled collapse (C4) flip-chip applications. As the progress of miniaturization continues, selective formation of electrical connections becomes increasingly challenging. One structural quality that is often used is dissimilar conductive layers which serve barrier, adhesion, and seeding purposes among others. Consequently, etch-processing formation of specific connections can result in destructive removal of required electrical connections. Similarly, etch processing can also result in stopped etches due to unwanted oxide films which form a husk over the material to be etched.
As the progress of miniaturization also continues, the junction between a microelectronic device metallization and the electrical bump becomes increasingly large relative to the mass of the electrical bump. Consequently, junction disparities have an increasingly detrimental effect on electrical communication between the device and the electrical bump. One junction disparity relates to migration of the flip-chip tin, typically from Sn37Pb solder, toward the metallization. Another consequence of miniaturization is stress that builds up in the ball-limiting metallurgy due to the formation of tin-containing intermetallic structures between the metallization and the electrical bump.